This invention relates to an electrodeposition drum to be used for manufacturing metal foils such as copper foils, iron foils, stainless steel foils, etc. by means of electrodeposition.
Such type of known electrodeposition drum comprises an inner drum having grooves on the surface thereof to provide reduced area of contact with the internal surface of the outer skin and further a silver plating layer incorporated on the contact surface (Japanese Patent Publication No. 24507/1983); or comprises an outer skin at least having a plating layer such as of silver plating, platinum plating or gold plating on the internal surface (Japanese Patent Publication No. 60149/1986), in order to enhance electrical conductivity between the inner drum and the outer skin.
FIGS. 5 and 6 each show a typical structure of prior art electrodeposition drum.
In the illustrated structure, the electrodeposition drum (a) comprises an inner drum (1) made of carbon steel and the like and an outer skin (2) made of titanium and the like, which is fitted on the external surface of said inner drum by shrinkage fitting. The electrodeposition drum (a) has a shaft (b) connected to a driving source for rotating said drum (a) and rotatably supported by a pair of bearings (c,d). The lower portion of the electrodeposition drum (a) is immersed in an electrolytic solution (f) filled up in an electrolyte tank (e), and an electric current is flowed across the electrodeposition drum (a) as a cathode and an anode (g) disposed in the electrolyte tank (e), i.e. from the outer skin (2) to the inner drum (1), so that an electrodeposited metal layer (h) or metal foil may be formed on the portion of the external surface of the electrodeposition drum (a) while it is immersed in the electrolytic solution (f) as the electrodeposition drum (a) rotates. By removing the deposited metal layer (h) from the external surface of the electrodeposition drum (a) metal foil can continuously be manufactured.
In the above-described prior art (Japanese Patent Publication No. 60149/1986), shrinkage fitting of the outer skin (2) has been employed for improved bond or adhesion between the inner drum (1) and the outer skin (2) and decreasing contact resistance therebetween. However, only by the adhesion achieved by shrinkage fitting the contact between the external surface of the inner drum (1) and the internal surface of the outer skin (2) will inevitably be nonuniform. As shown in FIG. 7, gaps (R) will irregularly be formed between said two surfaces to cause nonuniform electrical conductivity, and the electrodeposited metal layer (h) or metal foil comes to have nonuniform thickness or undergoes anomalous deposition and discoloration due to local overheat, or so-called hot spot, and consequently the production speed cannot be accelerated since a large amount of electric current cannot flow therethrough.
In the electrodeposition drum of Japanese Patent Publication No. 24507/1983, irregular gaps (R) are also present between the two surfaces as shown in FIG. 8, and thus the electrical conductivity between the two surfaces can hardly be improved sufficiently.